To improve driving safety, remote sensors are installed on some vehicles to detect presence of nearby road objectives, primarily other vehicles. Once a road objective is detected and identified by control system of the sensors as potential threat to driving safety, the control system coupled with vehicle driving system may control the vehicle to act properly such as braking to avoid a possible collision. The control system may also alert driver with audio sound or flashing of an indicator to draw driver's attention. Such safety system upon remote sensors becomes very sophisticated in order to work reliably for a variety of road situations under all weather conditions. For example, radar type remote sensor is very good at detecting moving vehicle by measuring Doppler frequency shift. Ground scattering noise of radar signal can be easily filtered out. But, rain or snow could severely affect its performance.
As CMOS imaging chip is going cheaper, onboard digital camera may be used for remote sensing to improve driving safety. Because driver must focus his/her attention on the road in front while driving, it is not helpful by just providing captured images of onboard camera to driver. Reliable image recognition must be implemented to detect potential road hazard. Considering varying lighting conditions during day and very low light condition at night, it is very challenging for such image recognition to attain reliable and consistent performance. Active illumination and sophisticated image processing mechanism may be added onto the system to improve performance, thus rendering system cost going much higher. Taking the advantage that CMOS imaging chip can detect a portion of wavelength of near infrared light, CMOS imaging chip based night vision system can provide better view of road condition for night driving. But, unless HUD (Head Up Display) is used to display the image captured by the night vision system, frequently switching eyesight between the road the displayed image may cause driver eye fatigue and delay of response, thus creating another driving hazard. It is probably apparent that, now and in foreseeable future, HUD display is not affordable for most ground vehicles except few luxury cars.
It is to be emphasized that above driving safety systems or similar types are developed to fit on new model of vehicles. Installation of the system on existing vehicle or model without original design consideration for that will involve too much modification and technical confliction, thus either economically infeasible or technically impractical.
An alternative approach to above active sensing system is to use inter-vehicle communication to share moving data of vehicle such as location, speed, and direction and let each vehicle determine on its own potential collision under development after receiving moving data of nearby other vehicles. With advent of GPS (Global Positioning System), ground vehicle having a GPS receiver unit carried therewith could measure its location to a certain accuracy without having to rely on expensive inertial navigation system. Low cost of general GPS unit makes the approach very attractive and affordable. Vehicle with GPS location data constantly updated could send its latest location data to other vehicles through inter-vehicle communication. Other vehicle receives the location data and keeps tracking the location data received for the same vehicle. It can tell the location, speed and direction of nearby vehicle. With assistance of Geographic Information System (GIS), also referred as digital road map herein, it is to be determined whether a collision is under development. If a potential collision is confirmed, driver is alerted to avoid an actual collision from occurring. However, this approach is seriously thwarted by insufficient accuracy of GPS receiver, even more seriously by slow update rate of GPS measurement. Typical GPS receiver has best accuracy about 5-6 meters. Considering typical lane width ranging from about 2.7 meters to about 3.7 meters, it is insufficient to determine which lane of a multi-lane road vehicle is moving on. Lack of lane recognition due to insufficient accuracy of GPS receiver could not discriminate whether a vehicle at faster speed is going to pass by or cause a collision. Thus, warning for collision avoidance yields very high false alarm rate. Typical GPS receiver has update rate of GPS measurement once per several seconds. Considering fast dynamic changing of positions for vehicles on road, many accidents may start and end within seconds. The update rate of once per seconds is too slow to permit a potential collision to be detected on time. Thus, collision won't be avoided due to either warning issued afterward or insufficient time left for driver to respond. It is possible to use very sophisticated differential GPS (DGPS) technology to improve the positioning accuracy. But, such type of GPS receiver system is very expensive and is not realistically seen on most ground vehicles. Furthermore, update rate is sacrificed when a higher positioning accuracy is pursued. When higher update rate is pursued, each measurement suffering from signal-noise variation has less time to collect more signal data, thus having less positioning accuracy. The dilemma of positioning accuracy and update rate is a serious challenge for using GPS for road collision avoidance.
Therefore, it is believed that there is a demand for low cost road safety enhancement system that can be easily deployed on any existing ground vehicle, no matter whether such deployment is preconceived in original design of vehicle, and operationally friendly for driver to get acquainted with. Although GPS based collision avoidance through inter-vehicle communication seems a practical solution for the demand, its performance suffers detrimental effect caused by insufficient positioning accuracy and slow update rate of GPS receiver. Furthermore, only few vehicles equipped with sophisticated GPS receiver with good positioning accuracy and acceptable update rate would not make road safer even for those vehicles because other vehicles are not capable of reporting their locations accurately and timely. This reality issue points out that low cost of solution is vital for such effort to ripen desired advantages.
The information disclosed in this Background of the Invention section is only for the enhancement of understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.